Mercury levels in polar bears reveal a growing threat to human health.
If the earth were a patient, the Arctic would be one of its more revealing pulse points, and that’s one reason Nil Basu, an assistant professor of environmental health sciences, is drawn to the region. Chemicals like mercury, a toxic byproduct of fossil-fuel combustion, are accumulating rapidly in the polar North, and their presence there says something about the health of our planet, and of its inhabitants.
Cold air traps global pollutants such as mercury in the Arctic’s water and soil, and they build up in the food chain. Polar bears, who sit at the top of that chain, have accumulated enough mercury in their bodies to kill a human being. But the animals have found ways to adapt and live, and that intrigues Basu.
With the cooperation of biologists at the Canadian Wildlife Service, Denmark’s National Environmental Research Institute, and local indigenous groups, he and his colleagues in the University of Michigan Ecotoxicology Lab are examining tissue samples from polar bears, seals, and predatory birds to gain a clearer understanding of how mercury affects animal health and in turn may affect human health. “We extrapolate from wildlife,” Basu says, because he and his colleagues are unable to study brain tissue in living human beings.
By studying wildlife, the researchers have found numerous associations between exposures to low levels of mercury and changes in brain neurochemistry, and these appear to be linked to changes in neurobehavior—learning, memory, IQ, and motor function—which other scientists have observed in people who live in the high North.
“When we couple the evidence from wildlife with the evidence in humans, it’s clear that the concentrations of mercury in the Arctic are of health concern,” says Basu.
Basu is developing biological tools to assess the early effects of toxic chemicals. He wants to determine the level at which mercury concentrations become dangerous to animals and humans. To date, his findings indicate that no level of mercury— not even the extremely low levels deemed safe by regulatory guidelines—is good. Basu’s work is featured in the exhibition “Science at the Poles” at the UM Exhibit Museum, through April 2008.
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- Mercury is a naturally occurring element and is extracted from the ground primarily by burning fossil fuels
- In the past century, concentrations of mercury have increased 10 to 15 times in the Arctic
- Up to eight percent of pregnant women in the U.S. and up to 40 percent of wildlife are exposed to mercury at harmful levels
- The Mad Hatter in Alice in Wonderland was supposedly poisoned by mercury, which entered his body from the felt in his hat and caused him to behave oddly; in real life, this type of odd behavior is called erethism, and it’s an indicator of mercury poisoning